Reopened: Caching the result of readPixelsSupported

src/core/SkTHashCache.h

+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkTHASHCACHE_DEFINED
+#define SkTHASHCACHE_DEFINED
+
+#include "SkTypes.h"
+#include "SkTDynamicHash.h"
+
+template <typename T,
+typename Key,
+typename Traits = T,
+int kGrowPercent = 75 >
+class SkTHashCache : public SkNoncopyable {
+public:
+
+    SkTHashCache() {
+        this->reset();
+    }
+
+    ~SkTHashCache() {
+        this->clear();
+    }
+
+    T* find(const Key& key) const {
+        return fDict->find(key);
+    }
+
+    /**
+     *  If element already in cache, return immediately the cached value
+     */
+    T& add(const T& add) {
+        Key key = Traits::GetKey(add);
+        if (T* val = this->find(key)) {
+            return *val;
+        }
+
+        T* element = SkNEW_ARGS(T, (add));
+
+        fDict->add(element);
+
+        return *element;
+    }
+
+    int size() const {
+        return fDict->count();
+    }
+
+    void reset() {
+        this->clear();
+
+        fDict.reset(SkNEW(DictType));
+    }
+
+private:
+    typedef SkTDynamicHash<T, Key, Traits, kGrowPercent> DictType;
+
+    void clear() {
+        if (fDict.get()) {
+            typename DictType::Iter it(fDict.get());
+
+            while (!it.done()) {
+                SkDELETE(&(*it));
+                ++it;
+            }
+        }
+    }
+
+    SkAutoTDelete<DictType> fDict;
+};
+
+#endif  /* SkHASHCACHE_DEFINED */
+